What is the technology to improve the aroma of tea drinks?

Tea after hot water extraction, filtration, storage, preparation, sterilization and filling processes, especially tea after extraction and sterilization of high temperature, its aroma components loss or damage is more serious. The biggest problem with the quality of these drinks is the absence of the aroma of freshly brewed tea. Conventional extraction techniques cannot sufficiently soak and capture the aroma and flavor characteristics of tea, especially the head fragrance.
Aroma loss due to processing
The researchers analyzed the changes of aroma components of canned green tea beverage after sterilization and concluded that: after sterilization, the contents of cis-3-hexenol, linalool oxide and nerolinium tertiary alcohol in tea beverage decreased; The contents of geranyl and benzyl alcohol increased. The contents of β-violone, 4-vinylphenol and indole also increased significantly. This is because the ligands in the tea are heated and decomposed, resulting in the increase of compounds such as enols and benzyl alcohol, which destroys the balance of the aroma components of green tea, and ultimately leads to the production of hot soup taste.
Another study on the change of aroma during the processing of green tea beverage showed that the total amount of low boiling point aroma components, high boiling point aroma components and all aroma components after extraction by SDE method were reduced by 47.44%, 39.0% and 40.86%, respectively, compared with the treatment of compound fire green tea.
The FI index is smaller than that of refire treatment, the aroma quality is reduced, and the aroma quality is decreased. The study also showed that the higher the extraction temperature and the longer the extraction time, the greater the loss of aroma component content.
The influence of UHT sterilization on the aroma components of green tea raw materials is also very obvious. After the hot sterilization at 137℃ for 4 s, the total amount of low-boiling point aroma components increases, while the content of high-boiling point aroma components decreases, resulting in a decrease in the F-I index, the aroma quality decreases, and the cooked soup tastes obvious.
Instant tea and tea concentrate are processed through extraction, coarse filtration, cooling, fine filtration or centrifugation, vacuum concentration, blending, sterilization and spray drying. Traditional instant tea processing technology can lose too much tea flavor.
Research and production practice has proved that after hot water extraction, tea almost has the same fresh aroma concentration as freshly brewed tea, but in each subsequent process (such as extraction, filtration, thermal concentration, sterilization and spray drying, etc.), due to heating, vacuum, oxygen and pump transport and other reasons, each process has a loss of aroma, especially vacuum concentration and spray drying process. Resulting in the production of instant powder or tea concentrate, the aroma intensity is almost only 10% to 20% of freshly brewed tea. The most serious losses are the low-boiling volatile components with “fragrance” characteristics.
The study on the change of aroma of instant green tea during processing showed that after extraction, concentration and spray drying, the aroma components, aroma components and sensory flavor of green tea showed a significant decline trend.
Compared with the raw materials of green tea, the raw materials had 59 aroma components, the total aroma components of the extract lost 35.63%, and the aroma components retained 47. The total aroma components of concentrated juice lost 82.03%, and 35 kinds of aroma components were retained. After spray drying operation, the total amount of aroma components lost 94.78%, and only 6 kinds of aroma components were retained. The aroma of the finished instant green tea is almost gone, and its green tea aroma and flavor characteristics no longer exist.
Aroma improvement technique
1. The use of multi-variety green tea combination of new tea beverage aroma China’s vast tea producing areas, numerous varieties, diverse environmental conditions have formed tea of different flavors. Different tea varieties, origin, seasons, cultivation conditions, raw materials and different processing technology of the same tea have different effects on the aroma of tea, thus forming a unique tea flavor.
China’s main tea categories are: black tea, green tea, green tea and flower tea, among which green tea is the most common. Green tea is the most abundant tea in China. It is made of fresh leaves by three steps: killing (stir-frying or steaming), twisting and drying.
Some green teas have a fragrant and elegant character (head fragrance), some have a strong and long-lasting character (base fragrance), some have a tender aroma, and some have a nutty flavor. Therefore, the characteristics of different green tea varieties can be combined to create a new type of green tea beverage aroma, which is one of the effective measures to improve the aroma of tea beverages.
2. Ultrafiltration membrane and reverse osmosis membrane concentration instead of vacuum concentration Using the characteristics of reverse osmosis membrane, under the condition that the tea does not phase change, the purpose of tea concentration can be achieved, and the loss of tea aroma can be reduced to a certain extent, and the aroma quality of instant tea powder can be improved. In particular, the aroma of tea concentrate produced by the combination of UHT and aseptic filling technology is better than that of instant tea powder.
3. Use freeze-drying process to dry tea powder. First, 25% of tea concentrate juice is quick-frozen at -25 ℃, and the quick-freezing time is ≤ 2.5 h. Then, under the vacuum degree of 66.7 ~ 266.6Pa, the water in the material is sublimed from solid ice to steam, so that the material is dehydrated and dried. Freeze drying is considered to be an effective measure to reduce the loss of tea aroma.
The aroma components of oolong tea extract, dry powder and freeze-dried powder were analyzed by GC-MS. The results showed that 46 kinds of aroma components could be detected by dry powder, 52 kinds could be detected by freeze-dried powder and 52 kinds could be detected by extract. The flavor of the freeze-dried powder was better than that of the spray-dried powder.
4. High temperature refire treatment In the tea industry, the high temperature refire treatment of tea to improve the aroma of tea is considered to be an effective measure. The formation and change of aroma components of green tea during refire were studied. Besides pyrrole, pyrazines and furans, 3, 7-dimethyl-1, 5, 7-trioctenol and phenylacetaldehyde were also formed after refire.
Among them, methylpyrazine, 2, 5-dimethylpyrazine, 1-ethylpyrrole-2-aldehyde, 2-acetylpyrrole and saccharaldehyde were mainly produced. Small amounts of these compounds can significantly improve the aroma of green tea.
5. Adding aroma additives In order to make up for the aroma loss in the processing of tea drinks, instant tea powder or tea concentrate, the method of adding flavors, spices or aroma improvement additives, such as β-cyclodextrin, can compensate for or reduce the aroma loss in the processing of tea drinks to a certain extent.
6. “ARS” aroma improvement technology The principle of “ARS” technology is: In order to avoid the loss of the fragrance of tea or the special head fragrance of tea varieties during the production process, the special aroma extraction device (ARS) is first used to continuously separate and extract the aroma compounds in tea and tea water from the tea pulp composed of tea and water. The extracted tea aroma is cooled and refrigerated to maintain the best aroma quality. After being extracted, the tea pulp and tea water can be further separated, filtered and concentrated into tea concentrate by conventional technology.
Then, the extracted tea aroma liquid can be added by the following methods: re-mixing in the tea concentrate and then UHT and aseptic filling to produce tea concentrate; The tea concentrate is remixed and then spray-dried or freeze-dried to produce high-aroma instant tea powder; It is added in the tea powder mixing process to produce high aroma instant tea powder; In the production of tea drinks as a natural flavor enhancer added to produce high-flavor tea drinks.
“ARS” technology is used to process tea pulp to produce the aroma of tea extract, similar to the aroma of freshly brewed tea. GC analysis instrument was used to compare the tea extracts obtained by conventional extraction equipment and ARS technology. The results showed that the content (concentration) of aromatic substances in the tea extracts obtained by ARS technology was higher (especially the head fragrance).
When the aroma liquid is added back to the tea concentrate, the aroma concentrate is added, UHT sterilization and aseptic filling to make the tea concentrate, or spray drying to make the instant tea, the product exhibits excellent fresh, fragrant or floral aroma characteristics. In particular, the performance of tea concentrate products is particularly outstanding, which can maintain 85% to 90% of the aroma characteristics and intensity of tea.